1. Field of the Invention
The present invention relates to an electrolytic method for the simultaneous preparation of a diaryliodonium salt and an alkoxide salt comprising adding to the anode compartment of an electrolytic cell an aromatic compound, an iodoaromatic compound, a solvent and a first organic salt, adding to the cathode compartment a hydroxyalkyl compound and a second organic salt, and applying an electric potential to the anode and the cathode to form a diaryliodonium salt in the anode compartment and an alkoxide salt in the cathode compartment. The invention also relates to a method of producing an ester of an aromatic acid wherein a mixture of the diaryliodonium salt and alkoxide salt obtained as described above are carbonylated by the addition of carbon monoxide to form the ester.
2. Description of the Prior Art
Diaryliodonium salts have long been known and can be prepared by various methods known in the art summarized below (Beringer, et al, J. Amer. Chem. Soc. 75: 2705 (1953); ibid., 81: 342 (1959)).
(A) Coupling of two aromatic compounds with iodyl sulfate in sulfuric acid. EQU 4ArH+(IO).sub.2 SO.sub.4 +3H.sub.2 SO.sub.4 .fwdarw.2Ar.sub.2 I.sup.+ +2H.sub.3 O.sup.+ +4HSO.sub.4.sup.- PA1 (B) Coupling of two aromatic compounds with an iodate in acetic acid-acetic anhydride sulfuric acid. EQU 2ArH+IO.sub.3 +2H.sub.2 SO.sub.4 +2Ac.sub.2 O.fwdarw.Ar.sub.2 I.sup.+ +2HSO.sub.4.sup.- +4AcOH+[O] PA1 (C) Coupling of two aromatic compounds with an iodine (III) acylate in the presence of an acid. ##STR1## (D) Condensation of an iodoso compound, an iodoso diacetate or an iodoxy compound with another aromatic compound in the presence of an acid. ##STR2##
In some cases it has been possible to oxidize an iodo compound in situ and then to condense it with another aromatic compound: ##STR3##
Diaryliodonium salts have been utilized in the preparation of aromatic carboxylic acids and esters thereof by a variety of carbonylation processes well known in the art. One such carbonylation process reacts a diarylidonium salt with carbon monoxide and an alcohol in the presence of a palladium catalyst (e.g., Nippon Kagaku Kaishi No. 2:236-241 (1982), which is incorporated herein by reference). Another carbonylation process reacts diphenyliodonium bromide and carbon monoxide at 190 atm in methanol at 100.degree. C. in the absence of a catalyst (Davidson, et al, J. Chem. Soc.(A): 1616-17 (1968), which is incorporated herein by reference). In yet another process, a diaryliodonium salt is reacted with carbon monoxide in the presence of zero-valent palladium in a hydrocarbon acid reaction medium (e.g., U.S. Pat. No. 4,564,701 to Lentz, et al, which is incorporated herein by reference). In yet another process, a diaryliodonium salt is reacted with carbon monoxide and water and an alcohol or amine in a basic reaction medium having a pK.sub.b greater than about 8 (e.g., U.S. Pat. No. 4,594,445 to Lentz, et al, which is incorporated herein by reference).
The aromatic acids and esters thereof are useful as intermediates in the synthesis of polyesters such as poly(ethylene terephthalate) and other useful polymeric materials.
The availability of the various aforementioned methods for the preparation of diaryliodonium salts, notwithstanding, there remains a need for an improved method and in particular a method of simultaneously producing a diaryliodonium salt and an alkoxide salt.